1. Field of the Invention
This invention relates broadly to medical canalicular inserts. More particularly, this invention relates to canalicular plugs which are placed into the punctal opening of the lacrimal duct to prevent lacrimal fluid from flowing through the lacrimal duct.
2. State of the Art
A variety of eye problems are related to an insufficient volume of tears on the surface of the eyes. The most common is keratoconjunctivitis sicca, also known as dry eyes. Contact lens problems are also often provoked by a lack of tear volume. A common cause for the insufficient tear volume is the drainage of tear fluid through the punctal opening of the lacrimal duct and into the nasal passage, thereby removing the fluid from where it is needed at the eye surface. Furthermore, drainage of tear fluid through the lacrimal duct into the nasal passage is believed to be the cause of or associated with several additional problems such as post nasal drip, sinusitis, allergies, headaches, and snoring.
A number of methods for closing the punctal opening have been used to prevent drainage of tears through the lacrimal duct, including suturing, laser sealing, and plugging. Plugging with a canalicular plug, such as a punctum plug or a lacrimal plug, is the least severe solution, is relatively inexpensive, and is being performed with increasing frequency.
Referring to prior art FIG. 1, a punctum plug 10 typically includes an elongate member or shaft 12 having a proximal end 14 and a distal end 16, a head 18 at the proximal end 14 of the shaft 12, and a relatively larger body 20 at the distal end 16 of the shaft 12 for occluding a lacrimal duct 22. The plug 10 is usually provided with a proximal axial bore 24 for receiving an insertion tool. In the punctum plug insertion procedure, the insertion tool is positioned into the bore 24 of the plug 10, the body 20 of the plug 10 is directed at a punctal opening 26 of the lacrimal duct 22, and force is applied to the insertion tool to move the body 20 of the plug 10 through the punctal opening 26, the muscles of the punctal ring 27, and into the vertical punctum 28 of the lacrimal duct 22. Once the plug 10 is fully inserted in the punctum 28, the insertion tool is removed. The plug 10 is fully inserted when the head 18 seats against the tissue at the punctal opening 26 and the body 20 seats within the lacrimal duct 22 so as to block the passage of tear fluid into the duct 22 and thereby retain tear fluid at the surface of the eye. Similarly, lacrimal plugs (not shown) which seat entirely within the lacrimal duct (completely below the punctal opening) are also known.
It has been found that prior art punctum and lacrimal plugs, while providing some benefit, often do not provide satisfactory occlusion of the lacrimal duct. Tear fluid tends to flow through the interstices 30 between the body of the plug and the tissue of the vertical punctum of the lacrimal duct. One proposed prior art solution of this problem has been to provide the plug 10 with an enlarged distal body 20. However, the punctum plug having the larger distal body is difficult to insert through the relatively small punctal opening and may inadvertently cause damage to the delicate punctal tissue.
Another problem with prior art punctum plugs is that the puncta of different individuals tend to be different in size. Thus, a physician is required to have available a plurality of differently sized punctum plugs. The physician must carefully measure or estimate :the size of the punctum and punctal opening of each patient to select the proper sized plug to insert. If the physician misjudges the size required, the punctum plug will not effectively block the lacrimal fluid flow and the patient will not realize the full benefit of the device.
It is therefore an object of the invention to provide a punctum plug which occludes the flow of tears through the lacrimal duct.
It is another object of the invention to provide a punctum plug which is not easily unintentionally dislodged from the lacrimal duct.
It is also an object of the invention to provide a punctum plug which is designed to facilitate insertion into the lacrimal duct.
It is a further object of the invention to provide a punctum plug which can easily be extricated by a physician when desired.
It is yet a another object of the invention to provide a single sized punctum plug which is adaptable to fit within substantially all sized puncta.
In accord with these objects, which will be discussed in detail below, a punctum plug generally includes a shaft and a head at a proximal end of the shaft. The distal end of the shaft terminates at a tip. The shaft is provided with at least one circumferentially radiating flexible anchoring arm of varying radial extension at at least two locations along its length which is adapted to secure the punctum plug within the punctum of a wearer.
The punctum plug of the invention is preferably made from a highly flexible, resilient biocompatible material. According to the invention, the head has a concave proximal surface and a distal surface which tapers toward the shaft. A diameter of the head of the plug is substantially larger than a diameter of the shaft. Preferably, the at least one flexible anchoring arm radially extends a distance greater than a radial width of the head. In accord with a first preferred aspect of the invention, the tip is no greater in diameter than the diameter of the shaft. An axial insertion bore is optionally defined through the proximal head of the plug extending a distance through the shaft.
According to a first embodiment of the invention, a plurality of anchoring arms in the form of symmetric circumferential rings are spaced a distance apart along a length of the shaft and define spaces therebetween. One or more of the rings has a diameter equal to or larger than the diameter of the head of the plug, and different rings preferably have different diameters.
According to a second embodiment of the invention, a plurality of anchoring arms in the form of longitudinally offset flanges are spaced a distance apart along a length of the shaft. The offset flanges are offset relative to a plane extending axially through the shaft providing an asymmetric cross-section to the plug at the shaft. Preferably, the flanges radially extend different lengths away from the shaft.
According to a third embodiment of the invention, the anchoring arm is a single flange helically wound about the shaft, and optionally the tip of the punctum plug. The radial length of the helical flange changes as it moves up or down the shaft. In addition, the pitch of the helical flange may change along the shaft.
According to a fourth embodiment of the invention, two preferably arcuate anchoring arms are provided at a distal portion of the shaft and extend outward and towards the head. The anchoring arms thereby function as barbs which retain the plug within the punctum.
According to a fifth embodiment of the invention, a single anchoring arm extends from the tip of the plug outward and upward toward the head of the plug. In addition, the arm is preferably relatively small adjacent the tip, to aid in insertion, and generally becomes relatively larger with its distance from the tip. The anchoring arm is flexible, and adapted to engage the underside of the punctal ring to secure the plug within the punctum.
In all embodiments, it is preferred that the arm or arm portion which extends the furthest radially be located at or along a middle portion of the shaft.
According to the invention, prior to insertion of the punctum plug into the punctum of a wearer, the punctal opening of the eye is optionally dilated. The plug is advanced into the punctum until the head of the plug rests adjacent the punctal opening. When the punctal opening returns to its predilated size, the anchoring arm or arms retain the punctum plug within the punctum and the head occludes the opening preventing lacrimal fluid flow. The anchoring arm or arms and the head surround the punctal ring to create a secure fit.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.